A is the answer. Reflection and rotation.
Nothing changes if you don't add anything.
Example:
10+10=20
20+0=20
nothing changes.
Let's use a for number of days when he shot 50 shots and b for number of days when he shot 100 shots.
We have:
a + b = 20
We also know that he shot total of 1250 shots:
50a + 100 b = 1250
We have two equations. We can solve them for a and b. Let's rearange first equation for a:
a= 20 - b
We insert this into second equation:
50 * (20 - b ) + 100b = 1250
1000 - 50b + 100b = 1250
50b = 250
b = 5
a = 20 - 5
a = 15
Mark shot 100 shots on 5 days.
(1/2) ^2 = 1/2 * 1/2 = 1/4
1/4 < 1/2
